Lee Chang-sub of the group BTOB. (Newsis)
Lee Chang-sub of the group BTOB. (Newsis)

BTOB member Lee Chang-sub has drawn attention after saying he developed gynecomastia as a side effect of taking hair loss medication.

The final installment of a trip to Shodoshima, Japan, featuring Lee, 2AM's Jung Jin-woon and Sistar's Soyou aired Wednesday on the KBS Joy variety show "Kkirikkiri."

In the episode, Lee's phone alarm went off at 10 p.m., signaling it was time to take his hair loss medication. "I have to take it at the same time every day," he said as he prepared the pills.

Watching this, Soyou asked why he was taking the medication when he already had a full head of hair. Lee replied, "It got this thick because I take it."

When Soyou, who said she was also losing a lot of hair, wondered whether she should start taking hair loss medication herself, Lee explained, "You need to take hair loss medication while you still have hair," adding, "The medication does not make hair grow back — it prevents hair from falling out."

However, Lee noted that the side effect for men is gynecomastia. "Breast tissue develops," he said. He went on to say, "I also developed breast tissue after taking it. With Jin-woon, even if he wears just one T-shirt, you can barely see his nipples poking out, but once you develop gynecomastia, your chest sticks out noticeably."

He added, "Later on, you have to get surgery to remove the tissue, but once you get rid of it, it never comes back."

In practice, gynecomastia has been reported as a side effect of some medications used to treat male pattern hair loss. Drugs such as finasteride and dutasteride, which work by inhibiting the conversion of testosterone into dihydrotestosterone (DHT), can rarely cause side effects including gynecomastia, breast pain and tenderness. In addition, sexual side effects such as reduced libido and erectile difficulties have also been reported due to changes in hormonal balance.

The Ministry of Food and Drug Safety strengthened its side-effect warnings for hair loss medications after reviewing a 2026 safety assessment from the European Medicines Agency, and now requires that this information be provided to medical staff and patients.


betterj@heraldcorp.com